Mobile communications are in continuous evolution and are already at the doorstep of a fifth generation (5G) era. As with previous generations, new use cases largely contribute in setting the requirements for new systems. Future networks may be designed with an emphasis on uniform user experience over an entire geographic area. Such a user experience may be exemplified by uniform achievable throughput, latency and/or reliability.
With respect to the issue of uniform experience, a wireless transmit/receive unit (WTRU) in a poor coverage area may use repetition to improve performance. However, repetition degrades achievable throughput and increases over-all latency. This is due, at least in part, from the fact that a repeating WTRU must use additional resources which could have been made available for use elsewhere. Additionally, the additional resources used by the repeating WTRU and not resources best spent because of the high likelihood that the WTRU will again fail to successfully retransmit in the poor coverage area.
For low power nodes, such as wireless sensors or massive low cost machine type communication (LC-MTC) devices, it is desirable that a battery of the device is long lasting, for example, many years. Repetition may prematurely drain the battery and cause an LC-MTC device to become unreachable or unable to continue transmitting. Furthermore, future networks may have a very high density of WTRUs. For example, sensor network deployments, wearables or at specific occasions, for example, a full stadium scenario, may lead to a highly dense layer of WTRUs. On the other hand, extreme rural scenarios exist wherein base station deployment may be minimal and far dispersed. Rural scenarios may be beneficial for a mobile operator since a low deployment cost may be a business goal.
Methods which leverage the high density of deployed WTRUs to improve a uniformity of a transmission or reception experience may be beneficial. Additionally, exploiting inherent features of a high density of deployed WTRUs may lead to benefits beyond making the experience of a WTRU more uniform. For example, in the example of massive broadband at a full stadium, it is possible that the data transmitted to many WTRUs is very similar. In such a scenario, it may be desirable to use the benefits of having multiple WTRUs closely located to improve the over-all performance.
In view of the above, more user-centric deployments may be beneficial. Such user centric deployments may be ad hoc and may be manifested as multiple cells cooperating, in one embodiment, in a transparent manner to a WTRU, or as multiple WTRUs in cooperation. WTRU cooperation may enable clusters of closely located WTRUs to improve individual performance by acting as a distributed antenna array. Therefore, WTRU cooperation may help exploit the advantages of dense clusters of WTRUs by improving cell edge WTRU performance, limiting over-all battery drain and also improving massive broadband transmission. Data redundancy may also be improved, since more copies of identical data may exist and be shared in the network.
To achieve beneficial WTRU cooperation, embodiments disclosed herein provide methods for determining how appropriate sets of WTRUs may cooperate. Furthermore, appropriate cooperation may require multiple WTRUs to efficiently share their data, for example, sharing of received data from an evolved Node B (eNB), or sharing of data to be transmitted by each WTRU to an eNB. Methods and systems for implementing efficient cooperative WTRU transmission are also addressed.